PROXIMAL PROMOTER ELEMENTS OF THE HUMAN ZETA-GLOBIN GENE CONFER EMBRYONIC-SPECIFIC EXPRESSION ON A LINKED REPORTER GENE IN TRANSGENIC MICE

We have investigated the transcriptional regulation of the human embry onic zeta-globin gene promoter. First, we examined the effect that del etion of sequences 5' to zeta-globin's CCAAT box have on zeta-promoter activity in erythroid cell lines. Deletions of sequences between -116 and -556 (cap = 0) had little effect while further deletion to -84 re duced zeta-promoter activity by only 2-3-fold in both transiently and stably transfected erythroid cells, Constructs containing 67, 84 and 5 56 bp of zeta-globin 5' flanking region linked to a beta-galactosidase reporter gene (lacZ) and hypersensitive site -40 (HS -40) of the huma n alpha-globin gene cluster were then employed for the generation of t ransgenic mice, LacZ expression from all constructs, including a 67 bp zeta-globin promoter, was erythroid-specific and most active between 8.5 and 10.5 days post-fertilisation. By 16.5 days gestation, lacZ exp ression dropped 40-100-fold. These results suggest that embryonic-spec ific activation of the human zeta-globin promoter is conferred by a 67 bp zeta-promoter fragment containing only a CCAAT and TATA box.